Description: The long-term goal of this laboratory is to understand the contributions made by the primate's cerebral cortex to the control of motor behavior. Current experiments are focused on the role of the rhesus monkey's frontal eye field (FEF) in the generation of eye movements. The FEF is a cortical region that is closely tied to sensorimotor processing. The FEF is found in both human and non-human primates and appears to be particularly important for eye movements that are driven by cognitive processes, for example, when a saccade is made to a remembered location or for the patterns o eye movements generated during reading or the examination of a complex visual scene. The FEF contains neurons whose firing is related to the generation of saccades, and projects to the superior colliculus as well as to other oculomotor regions of the brainstem. This project has three components designe to increase our understanding of FEF function in the generation of individual saccades, including contributions to initiation, velocity and amplitude, as well as in the planning of generation of complex sequences of saccades such as those used to survey a visual scene. In the first component, we will employ a behavioral paradigm developed in our laboratory to evoke natural scanning eye movements. In this paradigm, eye movements and neural activity can be recorded while a monkey freely views projected visual images. For the current project, we intend to examine this behavior before and after the injection of GABAergic drugs in the FEF. This manipulation will help to reveal FEF contributions to natural scanning eye movements either by the short-term removal of FEF input, with the inhibitory drug muscimol, or by making the FEF temporarily hyperactiv with the excitatory drug bicuculline. In the second component we will use the same microinjection techniques to examine the activity of saccade-related cell in the superior colliculus before and after the inhibition or excitation of FE input to the colliculus by microinjection. Comparing the resultant eye movemen behavior to changes in collicular cell activity will enhance our understanding of both the FEF and collicular contribution to the generation of these movements. In the third component, we will attempt to enhance our understandin of the functional organization of the FEF by using electrophysiological and anatomical techniques to generate a complete topographical map of the organization of saccade vectors in the FEF. This map will serve as an invaluable tool for future studies of the FEF. Because of known and expected similarities between rhesus monkey and human oculomotor cortex, these experiments will also provide a model for the functional organization of the cortical control of voluntary movement in humans.